You might want to check out the Givi Gold Series line of soft luggage. I just finished a week-end trip using the panniers, tail bag and small tank bag. I got these from RL Motorcycles. Great shop.
The bags fit well with a bit of a penny tech mindset. FWIW, I just used the combination of the buckle strap and the 2 velcro straps over (and under) the back seat for the panniers. I used a couple of small bungees to secure the panniers front and back using tie points on the bike (e.g., hooked to the "loop" on the passenger foot peg mounts.
I am somewhat of a stickler for looks and balance, so I got a $25 tool bag that I attach to the left side passenger grab rails. I use this for road supplies I don't expect to use frequently. But it also "fills out" the left side almost exactly like the right side muffler guard. So when I put the panniers on, they are very balanced, which makes me
Also, with this arrangement, I don't have to use any kind of rack or mounting systems. Makes it easy to take the bags off at the end of the day.
The tail bag has any number of ways to mount on the stock rack, including a velcro strap, bungee hooks, etc. With the panniers and the tail bag, this still leaves room for a sleeping bag, or other small bag that you want to carry.
A note on the color. When I odered these, they lloked silver, and I thought that they would be a perfect fit for my '07 silver wee. I should have thought more about the Gold Series name. While they are "carbon fiber" in color, they have a cold tint to them, that, while not objectionalble, is not a perfect match for the machine paint. Check out the link below.
Anyway, I am pretty happy with my purchase, because I got all 4 pieces, with shipping, for less than $340.